Fluid and Electrolytes & Renal Disorders

Transcription

1 Fluid and Electrolytes & Renal Disorders Topics for the Day Fluids and Electrolytes: review of normal physiology * Fluid imbalances * Electrolyte Disturbances * Beginning acid-base imbalance * Renal Disorders Fluid Types * Electrolytes Solutes that form ions (electrical charge) Cation (+) Anion (-)( Major body electrolytes: Na+, K+, Ca++, Mg++ Cl-,, HCO 3 -,, HPO 4 --,, SO 4 - Fluid & Electrolytes Fluid: Water Electrolytes: ions dissolved in water Sodium, potassium, bicarbonate, etc. Also used medically for non ions (glucose) Osmolarity osmols/kg solvent Osmolality osmols/liter solution In clinical practice are used interchangeably Electrolyte Distribution Major ICF ions K+ HPO 4 -- Major ECF ions NA+ CL-,, HCO 3 - Intravascular (IVF) vs Interstitial (ISF) Similar electrolytes, but IVF has proteins 1

2 Mechanisms Controlling Fluid and Electrolyte Movement Diffusion Selective Permeability Facilitated diffusion Active transport Osmosis 2*Na + BUN + Glucose/18 Hydrostatic pressure Oncotic pressure Cells are selectively permeable Sodium is the largest Determinant of Osmolality Na+: meq/l Ca+: meq/l K+: meq/l Osmolality~ ~ 2*(Na+) = 2*( meq/l) Normal (Isotonic) Low (hypotonic) < 280 High (hypertonic) > 300 2

3 Fluid Exchange Between Capillary and Tissue: Sum of Pressures Fluid Shifts Plasma to interstitial fluid shift results in edema Elevation of hydrostatic pressure Decrease in plasma oncotic pressure Elevation of interstitial oncotic pressure Fig Fluid Movement between ECF and ICF Water deficit (increased ECF) Associated with symptoms that result from cell shrinkage as water is pulled into vascular system Water excess (decreased ECF) Develops from gain or retention of excess water Fluid Spacing First spacing: Normal distribution of fluid in ICF and ECF Second spacing: Abnormal accumulation of interstitial fluid (edema) Third spacing: Fluid accumulation in part of body where it is not easily exchanged with ECF (e.g. ascites) Regulation of Water Balance F&E Balance Hypothalamic regulation Pituitary regulation Adrenal cortical regulation Renal regulation Cardiac regulation Gastrointestinal regulation Insensible water loss Renin Angiotensin I Angiotensin II Aldosterone Epinephrine Atria (ANP) Ventricles (BNP) Endothelium (CNP) 3

4 Fluid Status Indicators Physical exam Mucous membranes Turgor Blood Hematocrit Plasma BUN Urine Output (volume) Specific Gravity* < < 1.003: less conc > > 1.030: more conc Electrolytes F&E Balance Fluids Normal Contracted Expanded Electrolytes (Sodium!!!) Isotonic Hypertonic Hypotonic Extracellular Fluid Deficit Causes Inadequate intake, diuresis, excess sweating, burns, diarrhea, vomiting, hemorrhage Treatment Stop underlying disorder Replace fluids appropriately Treat complications Hypotonic D5W ½ NS ½ NS (0.45%) Volume Deficit IV Fluids Crystalloids Colloids Isotonic Hypertonic Albumin Dextran FFP NS (0.9%) Lactated Ringer Plasmalyte 3% Saline D5W in ½ NS D10W Isotonic Deficit Electrolyte drinks Isotonic saline (0.9%) injection Hypertonic Deficit Drinking Water Hypotonic saline (0.45%) injection, D5W Hypotonic Deficit Isotonic Saline Hypertonic saline (3%) PRBCs 4

5 Extracellular Fluid Excess Causes The Three failures: heart, liver, kidney Treatment Remove fluid --> >???? Treat underlying disorder Electrolyte Normal Values (memorize!!!!!) Sodium Potassium Chloride Calcium 9 11 BUN Creatinine CO2 (really bicarb) ) Magnesium: Electrolyte Disorders: Signs & Symptoms (most common*) Electrolyte Sodium (Na) Potassium (K) Excess Hypernatremia Thirst CNS deterioration Increased interstitial fluid Hyperkalemia Ventricular fibrillation ECG changes CNS changes Weakness Deficit Hyponatremia CNS deterioration Hypokalemia Bradycardia ECG changes CNS changes Fatigue Electrolyte Electrolyte Disorders Signs and Symptoms Calcium (Ca) Magnesium (Mg) Excess Hypercalcemia Thirst CNS deterioration Increased interstitial fluid Hypermagnesemia Loss of deep tendon reflexes (DTRs) Depression of CNS Depression of neuromuscular function Deficit Hypocalcemia Tetany Chvostek s, Trousseau s signs Muscle twitching CNS changes ECG changes Hypomagnesemia Hyperactive DTRs CNS changes Hypernatremia Thirst, lethargy, agitation, seizures, and coma Impaired LOC Produced by clinical states Central or nephrogenic diabetes insipidus Reduce levels gradually to avoid cerebral edema Hypernatremia Treatment Treat underlying cause If oral fluids cannot be ingested, IV solution of 5% dextrose in water or hypotonic saline Diuretics if necessary 5

6 Hyponatremia Results from loss of sodium-containing fluids Sweat, diarrhea, emesis, etc. Or from water excess Inefficient kidneys Drowning, excessive intake Confusion, nausea, vomiting, seizures, and coma Treatment Oral NaCl If caused by water excess Fluid restriction is needed If Severe symptoms (seizures) Give small amount of IV hypertonic saline solution (3% NaCl) If Abnormal fluid loss Fluid replacement with sodium- containing solution Hyperkalemia High serum potassium caused by Massive intake Impaired renal excretion Shift from ICF to ECF (acidosis) Drugs Common in massive cell destruction Burn, crush injury, or tumor lysis False High: hemolysis of sample Hyperkalemia Weak or paralyzed skeletal muscles Ventricular fibrillation or cardiac standstill Abdominal cramping or diarrhea Treatment Emergency: Calcium Gluconate IV Stop K intake Force K from ECF to ICF IV insulin Sodium bicarbonate Increase elimination of K (diuretics, dialysis, Kayexalate) 6

7 Hypokalemia Low serum potassium caused by Abnormal losses of K + via the kidneys or gastrointestinal tract Magnesium deficiency Metabolic alkalosis Hypokalemia Most serious are cardiac Skeletal muscle weakness Weakness of respiratory muscles Decreased gastrointestinal motility Hypokalemia KCl supplements orally or IV Should not exceed 10 to 20 meq/hr To prevent hyperkalemia and cardiac arrest No Pee no Kay!!!!!!!!!!!!!!!!!!!!!!!!! Calcium Obtained from ingested foods More than 99% combined with phosphorus and concentrated in skeletal system Inverse relationship with phosphorus Otherwise Calcium Bones are readily available store Blocks sodium transport and stabilizes cell membrane Ionized form is biologically active Bound to albumin in blood Bound to phosphate in bone/teeth Calcified deposits Calcium Functions Transmission of nerve impulses Myocardial contractions Blood clotting Formation of teeth and bone Muscle contractions 7

8 Calcium Balance controlled by Parathyroid hormone Calcitonin Vitamin D/Intake Bone used as reservoir Hypercalcemia High serum calcium levels caused by Hyperparathyroidism (two thirds of cases) Malignancy (parathyroid tumor) Vitamin D overdose Prolonged immobilization Hypercalcemia Decreased memory Confusion Disorientation Fatigue Constipation Treatment Excretion of Ca with loop diuretic Hydration with isotonic saline infusion Synthetic calcitonin Mobilization Hypocalcemia Low serum Ca levels caused by Decreased production of PTH Acute pancreatitis Multiple blood transfusions Alkalosis Decreased intake Hypocalcemia Weakness/Tetany Positive Trousseau s s or Chvostek s s sign Laryngeal stridor Dysphagia Tingling around the mouth or in the extremities 8

9 Treatment Treat cause Oral or IV calcium supplements Not IM to avoid local reactions Treat pain and anxiety to prevent hyperventilation-induced induced respiratory alkalosis Phosphate Primary anion in ICF Essential to function of muscle, red blood cells, and nervous system Deposited with calcium for bone and tooth structure Phosphate Involved in acid base buffering system, ATP production, and cellular uptake of glucose Maintenance requires adequate renal functioning Essential to muscle, RBCs, and nervous system function Hyperphosphatemia High serum PO 3 4 caused by Acute or chronic renal failure Chemotherapy Excessive ingestion of phosphate or vitamin D Calcified deposition: joints, arteries, skin, kidneys, and corneas Neuromuscular irritability and tetany Hyperphosphatemia Management Identify and treat underlying cause Restrict foods and fluids containing PO 3 4 Adequate hydration and correction of hypocalcemic conditions Hypophosphatemia Low serum PO 3 4 caused by Malnourishment/malabsorption Alcohol withdrawal Use of phosphate-binding antacids During parenteral nutrition with inadequate replacement 9

10 Hypophosphatemia CNS depression Confusion Muscle weakness and pain Dysrhythmias Cardiomyopathy Hypophosphatemia Management Oral supplementation Ingestion of foods high in PO 3 4 IV administration of sodium or potassium phosphate Magnesium 50% to 60% contained in bone Coenzyme in metabolism of protein and carbohydrates Factors that regulate calcium balance appear to influence magnesium balance Magnesium Acts directly on myoneural junction Important for normal cardiac function Hypermagnesemia High serum Mg caused by Increased intake or ingestion of products containing magnesium when renal insufficiency or failure is present Hypermagnesemia Lethargy or drowsiness Nausea/vomiting Impaired reflexes*** Respiratory and cardiac arrest 10

11 Hypermagnesemia Management Prevention Emergency treatment IV CaCl or calcium gluconate Fluids to promote urinary excretion Hypomagnesemia Low serum Mg caused by Prolonged fasting or starvation Chronic alcoholism Fluid loss from gastrointestinal tract Prolonged parenteral nutrition without supplementation Diuretics Hypomagnesemia Confusion Hyperactive deep tendon reflexes Tremors Seizures Cardiac dysrhythmias Hypomagnesemia Management Oral supplements (MgO, MgSO 4 ) Increase dietary intake Parenteral IV or IM magnesium when severe Elemenary Acid-Base balance Buffer systems Carbonic Acid Bicarbonate Metabolic: bicarb low metabolic acidosis high metabolic alkalosis Respiratory: carbon dioxide Metabolic Panel and acid-base CO2 on a BMP means bicarb!!!!!! normal <22 =? >26 =? 11

12 Metabolic Acidosis Manifestat Acidosis causes HYPERKALEMIA!!! Neuro: : Drowsiness, Confusion, H/A, coma CV: BP, dysrhythmia (K+), dilation GI: NVD, abd pain Resp: increased resp (comp) Metabolic Alkalosis Manifestat Alkalosis causes HYPOKALEMIA!!! Neuro: : Dizziness, Irritability, Nervous, Confusion CV: HR, dysrhythmia (K+) GI: NV, anorexia Neuromuscular: Tetany, tremor, paresthesia, seizures Resp: decreased resp (comp) MEMORIZE Arterial ph, PaCO2, HCO 3 -!!!!!!! Interpretation of ABGs Diagnosis in six steps Evaluate ph Analyze PaCO 2 Analyze HCO 3 Determine if Balanced or Unbalanced Determine if CO 2 or HCO 3 matches the alteration Decide if the body is attempting to compensate Interpretation of ABG 1. ph over balance 2. PaCO2 = respiratory balance 3. HC03- = metabolic balance 4. If all three normal = balanced 5. Match direction. e.g., if ph and PaCO2 are both acidotic,, then primary respiratory acidosis 6. If other is opposite, then partial compensation; if ph normal, then fully compensated. Interpretation of ABGs ph 7.36 PaCO 2 67 mm Hg PaO 2 47 mm Hg HCO 3 37 meq/l What is this? 12

13 Interpretation of ABGs ph 7.18 PaCO 2 38 mm Hg PaO 2 70 mm Hg HCO 3 15 meq/l What is this? Interpretation of ABGs ph 7.60 PaCO 2 30 mm Hg PaO 2 60 mm Hg HCO 3 22 meq/l What is this? Interpretation of ABGs ph 7.58 PaCO 2 35 mm Hg PaO 2 75 mm Hg HCO 3 50 meq/l What is this? Interpretation of ABGs ph 7.28 PaCO 2 28 mm Hg PaO 2 70 mm Hg HCO 3 18 meq/l What is this? Putting it all together Hypotonic D5W ½ NS ½ NS (0.45%) Always pay attention to Patient history Vital signs Symptoms and physical exam findings Lab Values Always ask: What is causing this abnormal finding? What can be done to fix it? Fluids Crystalloids Colloids Isotonic Hypertonic Albumin Dextran FFP NS (0.9%) Lactated Ringer Plasmalyte 3% Saline D5W in ½ NS D10W PRBCs 13

14 IV Fluids Purposes 1. Maintenance When oral intake is not adequate 2. Replacement When losses have occurred D5W (Dextrose = Glucose) Hypotonic Provides 170 cal/l Free water Moves into ICF Increases renal solute excretion Used to replace water losses and treat hyponatremia Does not provide electrolytes Normal Saline (NS) Isotonic No calories More NaCl than ECF 30% stays in IVF 70% moves out of IV space Normal Saline (NS) Expands IV volume Preferred fluid for immediate response Risk for fluid overload higher Does not change ICF volume Blood products Compatible with most medications Lactated Ringer s Isotonic More similar to plasma than NS Has less NaCl Has K, Ca, PO 3 4, lactate (metabolized to HCO 3 ) CONTRAINDICATED in lactic acidosis Expands ECF D5 ½ NS Hypertonic Common maintenance fluid KCl added for maintenance or replacement 14

15 D10W Hypertonic Max concentration of dextrose that can be administered in peripheral IV Provides 340 kcal/l Free water Limit of dextrose concentration may be infused peripherally Plasma Expanders Stay in vascular space and increase osmotic pressure Colloids (protein solutions) Packed RBCs Albumin Plasma Dextran 15